Organic peroxyacids are useful as fabric bleaching agents but are highly reactive compounds of limited storage stability. One such organic peroxyacid is the nonylamide of peroxyadipic acid ("NAPAA"). A problem encountered during development of NAPAA was its low AvO, or available oxygen, in a hard water wash solution. Not all of the NAPAA dissolves when detergent with bleach granules (including NAPAA) is added to the wash water. Surprisingly, by keeping the mean particle size of the crystallitic NAPAA less than about 260 microns, solubility of NAPAA is improved, even when the NAPAA crystals are incorporated in bleach granules before addition as part of a detergent or bleach composition to the wash water. It is believed that this is because the small NAPAA crystals do not complex easily with the calcium ions in hard water washes.
It has also been found that better thermal stability is achieved if boric acid is not added to the NAPAA, even though exotherm control agents, such as boric acid, are normally added to organic peroxyacids during synthesis to prevent an exotherm reaction.
It has also been found that additional chelants are not necessary to achieve a stable bleach granule where the NAPAA has been phosphate buffer washed.
The following patents and patent applications disclose information known about NAPAA and/or peracid particle size. U.S. Pat. No. 4,259,201, Cockrell, Jr. et al, issued Mar. 31, 1981 discloses granular detergent compositions containing organic peroxyacids which are buffered to a pH of 8.5-8.6 in water of about 2 grains hardness and no less than about 8 in water of about 14 grains hardness, preferably by using boric acid.
U.S. Pat. No. 4,126,573, Johnston, issued Nov. 21, 1978 discloses improved peroxyacid bleaching particles comprising an inner core of a solid peroxyacid compound and as a coating a surfactant compound. Methods of making and using such particles and compositions containing such particles are also described. The amount of surfactant used to coat the peroxyacid particles is from about 5 to 100% based on the weight of the peroxyacid. The coated particles have a particle diameter of from about 1 to 150 microns, preferably about 5 to 100 microns.
U.S. Pat. No. 4,818,425, Meijer et al, issued Apr. 4, 1989 discloses a process for preparation of agglomerates containing diperoxydodecanedioic acid (DPDA) and a water-impermeable material, e.g. lauric acid. The process comprises the successive steps of (1) agitating an aqueous suspension of the diperoxy acid in the presence of the water-impermeable material and above the melting point thereof, (2) cooling the suspension of the agglomerated particles thus obtained to a temperature at which the water-impermeable material turns solid, and (3) isolating the resulting agglomerates. According to Meijer et al, the greatest dimension of the suspended DPDA particles should be in the range of 0.5 to 100 microns, preferably 0.5 to 50 microns.
U.S. Pat. No. 4,634,551, Burns et al, issued Jan. 6, 1987, discloses bleaching compounds and compositions comprising fatty peroxyacids, salts thereof, and peroxyacid precursors having amide moieties in the fatty acid chain. NAPAA and NAPSA are included.
U.S. Pat. No. 4,686,063, Burns, issued Aug. 11, 1987, discloses fatty peroxyacids, or salts thereof, having amide moieties in the fatty chain and low levels of exotherm control agents. Control of the exotherms of NAPAA and NAPSA with boric acid are included (see column 10).
U.S. Pat. No. 4,909,953, Sadlowski et al, issued Mar. 20, 1990, discloses the use of a phosphate buffer wash for improved amide peroxyacid storage stability. Example I concerns NAPSA and Example III discusses NAPAA.
European Pat. No. Application 0 238 341, discloses a granular bleach activator composition containing an organic binder which has improved low temperature release properties by incorporating a water-soluble granule disintegration aid, usually a sequestering agent. A process for producing the granules is also provided. According to page 11, the activator should be provided in the form of small particles generally having an average particle size in the range of 50-500 microns, preferably 100-300 microns. The particulate binder preferably has an average particle size below 200 microns, generally below 100 microns, and is preferably free of particles above 200 microns in size. The granules preferably have an average particle size of 300-1500 microns, preferably 500-1000 microns.